String instruments, in particular violins and violas, are held, while being played, on their resonance-box end between the musician's chin and shoulder. As this causes, in the long run, for the musician a very uncomfortable position of the instrument, so-called chin rests and shoulder rests for violins and violas were developed.
These shoulder rests are detachably fixed, by means of a holding device, at the resonance box of the instrument and thus serve for making the holding of the instrument more comfortable for the musician. In general, a shoulder rest is fastened on a violin or the like, forming a support surface resting on the musician's shoulder, the instrument itself being supported on a selected level which depends on the musician's stature, in particular on the length of his or her neck.
Although numerous shoulder rests have been proposed and are available on the market, the types with a firm bottom, shaped according to the musician's shoulder, are preferred by a considerable part of the market. The underside of the firm bottom is usually provided with a pad resting against the musician's shoulder when the instrument is played. On the two ends of the bottom, holding elements or carrying elements rising upwards are mounted, which carry pivotable, forked end pieces. The latters can be fixed on the side walls of the resonance box of the instrument near the resonance-box bottom. To firmly fix this type of shoulder rest on the instrument, the bottom of the shoulder rest possesses a certain intrinisic elasticity serving for generating a certain clamping force with which the forked end pieces grasp the instrument. End pieces are also known in other embodiments in combination with the carrier elements, almost all of them, however, grasping the instrument with a certain clamping force.
To achieve a better adaption of the height level to the musician's neck, adapter pieces for shoulder rests have been developed. On the one hand, the shoulder rest is fixed to these adapter pieces, and on the other hand, the adapter piece is fastened to the instrument. Thus, the height of the instrument can be adapted by means of the adapter, to which shoulder rests of a simpler design, such as, for example, those with a simple flexible shoulder strap as shoulder support, can also be fixed.
These adapter pieces are often made of plastics or else of a lightweight metal, in order not to add too much weight. Such adapter pieces are in most cases fixed on the instrument, like the above-mentioned shoulder rests, by means of holding elements with end pieces, making use of certain clamping forces, near the bottom at the side of the resonance box of the instrument or at an angle over the edge of the resonance-box bottom. In most cases, such adapter pieces are braced in transverse direction relative to the longitudinal axis of the instrument at the widest spot of the resonance box or slightly diagonally to that spot.
The warpings which the adapter piece causes on the instrument are detrimental in this case because they result in a considerable impairment of the tonal quality. This is also valid for the so-called shoulder rests fixed through clamping forces. Furthermore, such a fixing of the adapter piece is not very stable, and when played in a very virtuoso way, the instrument tends to tilt or becomes partly detached from the holding elements. Adapter pieces from which the instrument will not be detached so easily are fixed under the resonance-box bottom almost over the entire surface, and their outer areas project over the resonance box of the instrument. This, however, hinders the musician in playing the instrument and, in addition, an adapter piece covering the entire surface considerably impairs the tonal quality of the instrument.